Crystalline N-hydroxyamino-acid derivatives 4, readily available from non-chiral acyl chlorides 2 and sultams 1, were treated with aldehydes in the presence of NaBH3CN to give N-alkylhydroxylamines 5. N,O-Hydrogenolysis of 5 and saponification of 6 furnished (S)-N-alkylamino acids 7 in high optical purity. Similarly, (R)-N-alkylamino acids 12 were obtained from the antipodal acylsultams 8.